The subject matter of the present application relates to microelectronic packages and assemblies incorporating microelectronic packages.
Semiconductor chips are commonly provided as individual, prepackaged units. A standard chip has a flat, rectangular body with a large front face having contacts connected to the internal circuitry of the chip. Each individual chip typically is contained in a package having external terminals connected to the contacts of the chip. In turn, the terminals, i.e., the external connection points of the package, are configured to electrically connect to a circuit panel, such as a printed circuit board. In many conventional designs, the chip package occupies an area of the circuit panel considerably larger than the area of the chip itself. As used in this disclosure with reference to a flat chip having a front face, the “area of the chip” should be understood as referring to the area of the front face.
In “flip chip” designs, the front face of the chip confronts the face of a package dielectric element, i.e., substrate of the package, and the contacts on the chip are bonded directly to contacts on the face of the substrate by solder bumps or other connecting elements. In turn, the substrate can be bonded to a circuit panel through the external terminals that overlie the substrate. The “flip chip” design provides a relatively compact arrangement; each package occupies an area of the circuit panel equal to or slightly larger than the area of the chip's front face, such as disclosed, for example, in certain embodiments of commonly-assigned U.S. Pat. Nos. 5,148,265; 5,148,266; and 5,679,977, the disclosures of which are incorporated herein by reference. Certain innovative mounting techniques offer compactness approaching or equal to that of conventional flip-chip bonding. Packages that can accommodate a single chip in an area of the circuit panel equal to or slightly larger than the area of the chip itself are commonly referred to as “chip-scale packages.”
Size is a significant consideration in any physical arrangement of chips. The demand for more compact physical arrangements of chips has become even more intense with the rapid progress of portable electronic devices. Merely by way of example, devices commonly referred to as “smart phones” integrate the functions of a cellular telephone with powerful data processors, memory and ancillary devices such as global positioning system receivers, electronic cameras, and local area network connections along with high-resolution displays and associated image processing chips. Such devices can provide capabilities such as full internet connectivity, entertainment including full-resolution video, navigation, electronic banking and more, all in a pocket-size device. Complex portable devices require packing numerous chips into a small space. Moreover, some of the chips have many input and output connections, commonly referred to as “I/Os.” These I/Os must be interconnected with the I/Os of other chips. The components that form the interconnections should not greatly increase the size of the assembly. Similar needs arise in other applications as, for example, in data servers such as those used in internet search engines where increased performance and size reduction are needed.
Semiconductor chips containing memory storage arrays, particularly dynamic random access memory chips (DRAMs) and flash memory chips are commonly packaged in single-chip or multiple-chip packages and assemblies. Each package has many electrical connections for carrying signals, power and ground between terminals and the chips therein. The electrical connections can include different kinds of conductors such as horizontal conductors, e.g., traces, beam leads, etc., which extend in a horizontal direction relative to a contact-bearing surface of a chip, vertical conductors such as vias, which extend in a vertical direction relative to the surface of the chip, and wire bonds that extend in both horizontal and vertical directions relative to the surface of the chip.
Besides minimizing the planar area of the circuit panel occupied by microelectronic assembly, it is also desirable to produce a chip package that presents a low overall height or dimension perpendicular to the plane of the circuit panel. Such thin microelectronic packages allow for placement of a circuit panel having the packages mounted therein in close proximity to neighboring structures, thus reducing the overall size of the product incorporating the circuit panel.
In light of the foregoing, certain improvements can be made to multi-chip microelectronic packages and assemblies in order to improve electrical performance. These attributes of the present invention can be achieved by the construction of the microelectronic packages and assemblies as described hereinafter.